An effective Pd nanocatalyst in aqueous media: stilbene synthesis by Mizoroki–Heck coupling reaction under microwave irradiation

• Carolina S. García,
• Paula M. Uberman and
• Sandra E. Martín

Beilstein J. Org. Chem. 2017, 13, 1717–1727, doi:10.3762/bjoc.13.166

• the galvanostatic electrolysis. After completion of the reaction the aqueous dispersion of Pd NPs was placed in a 25 mL volumetric flask to be used as catalyst solution for Mizoroki–Heck coupling reaction without further purification. Average dimensions and shapes of Pd NPs were determined by

1-Imidoalkylphosphonium salts with modulated C_α–P⁺ bond strength: synthesis and application as new active α-imidoalkylating agents

• Jakub Adamek,
• Roman Mazurkiewicz,
• Anna Węgrzyk and
• Karol Erfurt

Beilstein J. Org. Chem. 2017, 13, 1446–1455, doi:10.3762/bjoc.13.142

• 6 (3.0 mmol) and silica gel-supported piperidine (SiO2-Pip; 200 mg, 0.22 mmol) were added. The electrolysis was carried out under stirring at a current density of 0.3 A/dm2 at 0 °C until a 2.7–3.75 F/mol charge had passed. Solid SiO2-Pip was filtered off, methanol was evaporated under reduced

Diastereoselective anodic hetero- and homo-coupling of menthol-, 8-methylmenthol- and 8-phenylmenthol-2-alkylmalonates

• Matthias C. Letzel,
• Hans J. Schäfer and
• Roland Fröhlich

Beilstein J. Org. Chem. 2017, 13, 33–42, doi:10.3762/bjoc.13.5

• . Keywords: anodic decarboxylation; diastereoselectivity; Kolbe electrolysis; radical hetero-coupling; radical homo-coupling; Introduction Intermolecular radical additions with high diastereoselectivity have been described for a number of cases [1][2][3][4][5][6][7][8][9]. There are much fewer reports on

• the electrode surface [22]. The generation of radicals in a thin reaction layer at the electrode surface leads to high radical concentrations that favor bimolecular radical coupling. Electrolysis of equal carboxylic acids leads to a symmetrical dimer by homo-coupling of the radicals. Coelectrolysis of

• -coupling product of carboxylic acid 18 was found, but polar compounds were obtained, whose structures were not determined. To explain this failure, it is assumed that under the electrolysis conditions the electron-rich aromatic ring system is preferentially oxidized. Cyclic voltammetry of the malonates 15a

Electron-transfer-initiated benzoin- and Stetter-like reactions in packed-bed reactors for process intensification

• Anna Zaghi,
• Daniele Ragno,
• Graziano Di Carmine,
• Carmela De Risi,
• Olga Bortolini,
• Pier Paolo Giovannini,
• Giancarlo Fantin and
• Alessandro Massi

Beilstein J. Org. Chem. 2016, 12, 2719–2730, doi:10.3762/bjoc.12.268

• homogeneous conditions and their subsequent utilization in transesterification and amidation processes by the reaction telescoping approach [12]. Similarly, the group of Brown reported on the oxidative esterification and amidation of aldehydes in undivided microfluidic electrolysis cells mediated by

Continuous-flow synthesis of primary amines: Metal-free reduction of aliphatic and aromatic nitro derivatives with trichlorosilane

• Riccardo Porta,
• Alessandra Puglisi,
• Giacomo Colombo,
• Sergio Rossi and
• Maurizio Benaglia

Beilstein J. Org. Chem. 2016, 12, 2614–2619, doi:10.3762/bjoc.12.257

• conditions. Typically, the transformation of nitro compounds to amines under continuous-flow conditions is performed through the metal-catalyzed hydrogenation [21][22][23] with ThalesNano H-Cube®, which exploits H2 generated in situ by water electrolysis [24]. The procedure involves relatively mild reaction

Versatile deprotonated NHC: C,N-bridged dinuclear iridium and rhodium complexes

• Albert Poater

Beilstein J. Org. Chem. 2016, 12, 117–124, doi:10.3762/bjoc.12.13

• electron of the system, thus the expected mixed valent Ir(I)/Ir(II) species turns out to display two identical metal centres that distribute equally the cost of the electrolysis of 3. Geometrically no asymmetry is observed, and together with the positive charge increase of 0.306e on each former Ir(I

Polythiophene and oligothiophene systems modified by TTF electroactive units for organic electronics

• Alexander L. Kanibolotsky,
• Neil J. Findlay and
• Peter J. Skabara

Beilstein J. Org. Chem. 2015, 11, 1749–1766, doi:10.3762/bjoc.11.191

• electrolysis of 35 and 39 revealed that approximately two electrons were released per monomer unit; this is much more than one would expect from a simple PT that normally donates one electron per 3–10 thiophene units [80]. To the best of our knowledge, 35 is the most dopable polythiophene in the literature

A new method for the synthesis of α-aminoalkylidenebisphosphonates and their asymmetric phosphonyl-phosphinyl and phosphonyl-phosphinoyl analogues

• Anna Kuźnik,
• Roman Mazurkiewicz,
• Mirosława Grymel,
• Katarzyna Zielińska,
• Jakub Adamek,
• Ewa Chmielewska,
• Marta Bochno and
• Sonia Kubica

Beilstein J. Org. Chem. 2015, 11, 1418–1424, doi:10.3762/bjoc.11.153

• min by means of a rotating cathode before commencement of the oxidation. Electrolysis was carried out while stirring at 0.1 A until a 4.5–10 F/mol charge had passed (Table 2). After evaporation of the methanol in vacuo, the residue was extracted with CH2Cl2. Subsequent evaporation of the solvent from

• titanium, 1.2 cm2). Electrolysis was carried out while stirring at 0.1 A until a 4.5–10 F/mol charge had passed (Table 2). After evaporation of MeOH under reduced pressure, the residue was extracted with CH2Cl2 followed by further evaporation of the solvent from the extracts in vacuo to obtain diethyl 1-(N

Cathodic hydrodimerization of nitroolefins

• Michael Weßling and
• Hans J. Schäfer

Beilstein J. Org. Chem. 2015, 11, 1163–1174, doi:10.3762/bjoc.11.131

• at the acidic CH bond. Eight 1-aryl-2-nitro-1-propenes have been electrolyzed in an undivided electrolysis cell to afford 2,5-dinitro-3,4-diaryl hexanes in high yield. The 4-methoxy-, 4-trifluoromethyl-, 2-chloro- and 2,6-difluorophenyl group and furthermore the 2-furyl and 2-pyrrolyl group have been

• hydrodimerization is performed in a divided electrolysis cell by variation of the electrolyte (Table 1, Scheme 2). The working potential was chosen from cyclic voltammetry and current/voltage curves in the cell used for the preparative conversion. The potential in the controlled potential electrolysis was −0.9 V to

• expected to have a higher oxidation potential than DMF due to the nitro group the advantageous use of an undivided cell appears to be possible. Taking the optimal conditions of electrolysis Nr. 5 in Table 1 the influence of the parameters mentioned above was investigated (Table 2). The influence of the

Interactions between tetrathiafulvalene units in dimeric structures – the influence of cyclic cores

• Huixin Jiang,
• Virginia Mazzanti,
• Christian R. Parker,
• Søren Lindbæk Broman,
• Jens Heide Wallberg,
• Karol Lušpai,
• Adam Brincko,
• Henrik G. Kjaergaard,
• Anders Kadziola,
• Peter Rapta,
• Ole Hammerich and
• Mogens Brøndsted Nielsen

Beilstein J. Org. Chem. 2015, 11, 930–948, doi:10.3762/bjoc.11.104

• electrolysis of 1b, 4, 5, and 8. Not surprisingly, compound 1b, which showed no sign of electronic interactions between the TTF units in the CV (two two-electron oxidations), exhibited no CT absorption band during the oxidation from neutral to dication. Instead, compound 8, and, in part, compound 4 showed

• instrument settings to get good resolution. The UV–vis–NIR spectra were obtained using a Varian Cary 5E spectrophotometer in double beam mode. The controlled-potential electrolysis was carried out using a CH Instruments Model CHI630B potentiostat to manually adjust the potential. 4',5'-Bis(butylthio)-4

• •+–TTF → TTF•+–TTF•+. UV–vis–NIR absorptions of 1b (2.4 mM), 4 (3.5 mM), 5 (2.9 mM), and 8 (1.9 mM) in CH2Cl2 + 0.1 M Bu4NPF6 at different oxidation states (obtained by electrolysis of the neutral species in an Ottle cell, ultimately generating the tetracation). The insets show expansions of the NIR

Trifluoromethyl-substituted tetrathiafulvalenes

• Olivier Jeannin,
• Frédéric Barrière and
• Marc Fourmigué

Beilstein J. Org. Chem. 2015, 11, 647–658, doi:10.3762/bjoc.11.73

• extremely soluble, a consequence of the presence of the CF3 groups and there was no crystal growth on the anode. However, with 1c as electroactive donor molecule and (n-Bu4N)(FeCl4) as electrolyte, layering of the CH2Cl2 solutions after electrolysis with pentane afforded crystals of a 1:1 phase formulated

Highly selective generation of vanillin by anodic degradation of lignin: a combined approach of electrochemistry and product isolation by adsorption

• Dominik Schmitt,
• Carolin Regenbrecht,
• Marius Hartmer,
• Florian Stecker and
• Siegfried R. Waldvogel

Beilstein J. Org. Chem. 2015, 11, 473–480, doi:10.3762/bjoc.11.53

• . Electrolysis conditions are optimized regarding reaction temperatures below 100 °C allowing operation of aqueous electrolytes in simple experimental set-up. Employing ion exchange resins gives rise to a selective removal of low molecular weight phenols from the strongly alkaline electrolyte without

• using the most productive anode materials. Under the conditions described, the electrochemical process usually resulted in moderate yields of 1 <2.0 wt % per electrolysis run but the selectivity towards vanillin (1) formation is outstanding (Figure 1). The only other volatile byproduct formed in much

• to long electrolysis times. Three-dimensional electrodes are a suitable way to increase the effective anodic area leading to an improved space–time yield. For this reason 3D materials composed of different Ni-based materials were employed as electrode materials for the electrochemical process (Figure

Electrochemical oxidation of cholesterol

• Jacek W. Morzycki and
• Andrzej Sobkowiak

Beilstein J. Org. Chem. 2015, 11, 392–402, doi:10.3762/bjoc.11.45

• transformed to 25-hydroxycholesterol (2) in 13% yield (Scheme 1). The statement that the Tl(II)/HMP/O2 adduct, suggested to be a radical in nature, is responsible for cholesterol oxidation was based on the following observations. The electrolysis performed in the divided cell indicated that the oxidation of

• of a dimeric Fe(III)–Fe(V) manifold complex, (H2O)(PA)2Fe(III)–O–Fe(V)=O(PA)2, as an active intermediate that would work as a monooxygenating species for cholesteryl acetate. Indirect electrochemical oxidation of cholesterol was also reported by Wu et al. [36]. The electrolysis was performed under

• platinum plates. The electrolysis was performed in the presence of FeCl3 and hematoporphyrin (HMP), and dioxygen was constantly delivered to the cell. Three products, 5α,6β-dichlorocholestan-3β-ol (11), 6α-chlorocholestane-3β,5ß-diol (12), and epoxide (10), as a 1:3 mixture of α and β-isomers, were

Photovoltaic-driven organic electrosynthesis and efforts toward more sustainable oxidation reactions

• Bichlien H. Nguyen,
• Robert J. Perkins,
• Jake A. Smith and
• Kevin D. Moeller

Beilstein J. Org. Chem. 2015, 11, 280–287, doi:10.3762/bjoc.11.32

• (galvanostatic) electrolysis [4]. When a constant current is passed through an electrolysis cell, the potential at the anode increases until it reaches that of the substrate in solution with the lowest oxidation potential. It then remains constant at that potential until the effective concentration of the

• the reaction, over 90% of the initial substrate can be consumed before this loss of selectivity occurs. Hence, at low current densities a constant current electrolysis reaction automatically adjusts to the potential of the substrate to be oxidized and then remains at that potential for the majority of

• desired chemical transformation before returning to the anode as its reduced form. The process converts the chemical oxidant into a catalyst. Since the oxidant is not consumed during the reaction, the potential at the anode remains constant throughout the electrolysis. As in the direct oxidation, the

Cathodic reductive coupling of methyl cinnamate on boron-doped diamond electrodes and synthesis of new neolignan-type products

• Taiki Kojima,
• Rika Obata,
• Tsuyoshi Saito,
• Yasuaki Einaga and
• Shigeru Nishiyama

Beilstein J. Org. Chem. 2015, 11, 200–203, doi:10.3762/bjoc.11.21

• unprecedented neolignan-type dimeric compounds. Results and Discussion Cathodic reduction on BDD electrode The ester methyl cinnamate (1a) was electrolyzed under constant current electrolysis (CCE) conditions in a divided cell. Solvents used for the reactions played a significant role in providing the desired

Electrochemical selenium- and iodonium-initiated cyclisation of hydroxy-functionalised 1,4-dienes

• Philipp Röse,
• Steffen Emge,
• Jun-ichi Yoshida and
• Gerhard Hilt

Beilstein J. Org. Chem. 2015, 11, 174–183, doi:10.3762/bjoc.11.18

• -dienols were transformed into cyclic phenylselenoethers by intramolecular cyclisation using selenium cations generated by indirect electrolysis. The reaction was carried out by electrolysing a mixture of the 1,4-dienol, diphenyl diselenide and tetraethylammonium bromide in CH3CN at room temperature in an

• iodoalkoxylated products of type 5 (Scheme 3). The electrolysis was carried out in an H-type divided cell (4G glass filter) equipped with carbon fiber electrodes (see Supporting Information File 1). Each chamber was charged with 2,6-lutidine and TBABF4 in CH3CN (0.3 M) and additionally the 1,4-dienol and sodium

• iodide were placed in the anode chamber. The reaction was performed at constant current electrolysis (10 mA) at 0 °C. It is considerable that the presence of 2,6-lutidine is crucial for a successful reaction. In the absence of 2,6-lutidine only traces of the product can be observed and oxidation of the

3α,5α-Cyclocholestan-6β-yl ethers as donors of the cholesterol moiety for the electrochemical synthesis of cholesterol glycoconjugates

• Aneta M. Tomkiel,
• Adam Biedrzycki,
• Jolanta Płoszyńska,
• Dorota Naróg,
• Andrzej Sobkowiak and
• Jacek W. Morzycki

Beilstein J. Org. Chem. 2015, 11, 162–168, doi:10.3762/bjoc.11.16

• electrolysis of compounds 6a–h in the presence of 1,2:3,4-di-O-isopropylidene-α-D-galactopyranose (7) are shown in Scheme 2. In all of the experiments the ratio of sugar:cholesteryl donor was close to 1:1. The electrochemical reaction conditions were the same as those applied in our previous paper for the

• ), probably due to steric reasons. A limitation of the glycosylation process are the consecutive reactions of glycoconjugate 11 at a growing voltage and its limited stability under electrolysis conditions. The major decomposition product is 3β-O-(3’,4’-O-isopropylidene-α-D-galactopyranos-6’-yl)-cholest-5-ene

• , i.e., compound 11 loses one of the O-isopropylidene groups upon prolonged electrolysis. Although the electrochemical overoxidation of glycoconjugate 11 seems to be a minor problem at the initial steps due to a relatively large difference in the oxidation potentials and concentrations between

Highly selective electrochemical fluorination of dithioacetal derivatives bearing electron-withdrawing substituents at the position α to the sulfur atom using poly(HF) salts

• Bin Yin,
• Shinsuke Inagi and
• Toshio Fuchigami

Beilstein J. Org. Chem. 2015, 11, 85–91, doi:10.3762/bjoc.11.12

• without electrolysis overnight and 1b was mostly recovered (Table 2, entry 5). Therefor electrolysis is necessary for the fluorination to take place. Among the solvents tested for electrolysis, we decided to use MeCN for further studies on the anodic fluorination based on a good current efficiency and the

• rather low yields (Table 3, entry 5). The longer electrolysis caused the formation of complicated products. This result is quite different from the case of 1b and 1d (Table 2, entry 1 and Table 3, entry 1). Such different anodic behavior may be attributable to different pKa values of the α-proton of the

The Shono-type electroorganic oxidation of unfunctionalised amides. Carbon–carbon bond formation via electrogenerated N-acyliminium ions

• Alan M. Jones and
• Craig E. Banks

Beilstein J. Org. Chem. 2014, 10, 3056–3072, doi:10.3762/bjoc.10.323

• to the C–H activation of low reactivity intermediates. In this article, containing over 100 references, we highlight the development of the Shono-type oxidations from the original direct electrolysis methods, to the use of electroauxiliaries before arriving at indirect electrolysis methodologies. We

• electrolysis of carbamates to accumulate the N-acyliminium ion reactive intermediate then under non-oxidative conditions the nucleophile is introduced. Importantly, the nucleophile cannot be present when the N-acyliminium ion is being formed under electrochemical conditions, as in most cases it is easier to

• radicals from the cation pool method [24][25]. Indirect electrolysis methods The only indirect anodic oxidation method to perform the Shono-oxidation with a thiophenyl electroauxiliary has been reported by Fuchigami and co-workers [36]. Using a catalytic triarylamine redox mediator, anodic

Recent advances in the electrochemical construction of heterocycles

• Robert Francke

Beilstein J. Org. Chem. 2014, 10, 2858–2873, doi:10.3762/bjoc.10.303

• interesting and practical alternative to conventional methods for heterocycle synthesis [19][20]. Since toxic and hazardous redox reagents are either replaced by electric current (direct electrolysis) or generated in situ from stable and non-hazardous precursors (indirect electrolysis), electrosynthesis is

• categories are discussed in sections 1.4 and 2.4. A further important aspect is the type of electron transfer involved in the reaction. With regard to heterocycle synthesis, both direct electrolysis involving heterogeneous electron transfer between electrode and substrate as well as indirect electrolysis

• , resulting in N-tosylated pyrrolidine products (Scheme 2, X = NHTs) [35][36]. The reactions can be carried out under galvanostatic conditions (C.C.E. = constant current electrolysis) at room temperature in an undivided cell using a vitreous carbon anode. The presence of a proton scavenger is necessary in

Electrocarboxylation: towards sustainable and efficient synthesis of valuable carboxylic acids

• Roman Matthessen,
• Jan Fransaer,
• Koen Binnemans and
• Dirk E. De Vos

Beilstein J. Org. Chem. 2014, 10, 2484–2500, doi:10.3762/bjoc.10.260

• focused on the fixation of CO2 using sacrificial anodes [38][39][40] (Scheme 6a). The higher oxidation potential of sacrificial anodes compared to that of the other reaction species makes this setup readily compatible with a simple undivided electrolysis cell, without a membrane separating the catholyte

Thermodynamically stable [4 + 2] cycloadducts of lanthanum-encapsulated endohedral metallofullerenes

• Yuta Takano,
• Yuki Nagashima,
• M. Ángeles Herranz,
• Nazario Martín and
• Takeshi Akasaka

Beilstein J. Org. Chem. 2014, 10, 714–721, doi:10.3762/bjoc.10.65

• electron using bulk potential electrolysis for the NMR measurements. 1H NMR spectrum of the resulting anionic 5b ([5b]−) clearly illustrates the characteristic signals from the addend (Figure 13). Signals of the methylene protons appear as a sharp AB system at 4.55, 4.30, 2.94, and 2.82 ppm. The 13C NMR

Tuning the interactions between electron spins in fullerene-based triad systems

• Maria A. Lebedeva,
• Thomas W. Chamberlain,
• E. Stephen Davies,
• Bradley E. Thomas,
• Martin Schröder and
• Andrei N. Khlobystov

Beilstein J. Org. Chem. 2014, 10, 332–343, doi:10.3762/bjoc.10.31

• . Redox potentials were referenced vs the Fc+/Fc couple, which was used as an internal standard. Compensation for internal resistance was not applied. Bulk electrolysis Bulk electrolysis experiments at a controlled potential were carried out using a two-compartment cell. A Pt/Rh gauze basket working

• the test solution was stirred rapidly during electrolysis. Each solution contained [n-Bu4N][BF4] (0.2 M) as the supporting electrolyte and the compound under investigation (5 mL, 0.5 mM) and were prepared using Schlenk line techniques. Synthesis of the fullerene triads 4–6 Synthesis of 4 [60

Anodic coupling of carboxylic acids to electron-rich double bonds: A surprising non-Kolbe pathway to lactones

• Robert J. Perkins,
• Hai-Chao Xu,
• John M. Campbell and
• Kevin D. Moeller

Beilstein J. Org. Chem. 2013, 9, 1630–1636, doi:10.3762/bjoc.9.186

• not appear to be a significant competing pathway. Experimental results indicate that oxidation occurs at the olefin and that the reaction proceeds through a radical cation intermediate. Keywords: carboxylic acid; cyclization; electrolysis; free radical; kolbe; radical cation; Introduction Anodic

• taken because of the well-known Kolbe electrolysis reaction (Scheme 3) [10][11]. In the Kolbe electrolysis (Scheme 3, reaction 1), a carboxylic acid is oxidized. A decarboxylation reaction then leads to the formation of a radical that is subsequently trapped by a second radical formed in solution. The

• . Radical cation stabilization by an o-methoxy substituent. General scheme for anodic cyclization reactions. Anodic cyclization competition study. Kolbe electrolysis reactions. Oxidative coupling between a carboxylic acid and electron-rich olefin. Predicted relative rates of single-electron oxidation based

Asymmetric synthesis of a highly functionalized bicyclo[3.2.2]nonene derivative

• Toshiki Tabuchi,
• Daisuke Urabe and
• Masayuki Inoue

Beilstein J. Org. Chem. 2013, 9, 655–663, doi:10.3762/bjoc.9.74

• -dimethylbenzene-1,4-diol (3) and maleic anhydride lead to the construction of bicyclo[2.2.2]octene 4, which was then transformed into racemic 2 through electrolysis [11]. Alternatively, the Diels–Alder reaction between 3,6-dimethyl-o-quinone monoacetal 5 and 1,1-diethoxyethylene provided bicyclo[2.2.2]octene 6